The bottle cap was first patented and produced in the 1890's. The basic metal crown cap has not conceptually changed from that time. Conventional crown caps include a circular top, a circular skirt depending downwardly from a periphery of the top, and a downwardly and radially outwardly extending flange extending from a periphery of the skirt. The flange is fluted or serrated, and may be configured for either pry-off or twist off removal. Upon application of the cap to a bottle, the flutes are deformed to affix the cap to a bead or threads on the bottle's finish, and a thermoformed liner on the underside of the cap is pressed against the bottle's rim to enhance sealing.
The majority of crown caps used in the U.S. are twist off types that operate on new bottles that are not recycled. The majority of crown caps in many countries, however, are pry-off types that often operate on recycled bottles.
There is a general need for improved and lower weight crown caps.